Interior cabins of vehicles typically include cabin vents or pressure relief devices. Without such devices, air pressure inside the vehicle cabin could damage occupants' ear drums. Further, when a vehicle door is closed, air pressure within the vehicle needs to be relieved or the door will not close. If an air bag is activated in a vehicle that does not have a venting or pressure relief device, an occupant's ear drums may be damaged.
Pressure relief devices are usually hidden from view. For example, a pressure relief device may be found in a trunk or on a body frame pillar structure. Each pressure relief device is adapted to allow air to pass out of an enclosed structure, while also preventing a significant amount of air, dust, water or other contaminants into the enclosed area. Thus, pressure relief devices are, in essence, one-way valves or one-way check valves, and are configured to maintain a small amount of back pressure per customer specifications.
FIG. 1 illustrates an isometric view of a conventional pressure relief device 10. The pressure relief device 10 includes a plastic main body 12 having a plurality of air passages 14. A light membrane 16 is positioned over the air passages 14, and is configured to allow air to pass in one direction. In order to allow air to pass, the light membrane 16 opens off of the main body 12 in response to air flow. Typically, a seal (not shown) is provided around the main body 12 and acts to seal the hole in the mating structure (not shown) upon assembly. The seal is typically molded around the main body 12 in a secondary molding operation, or may be adhesively or chemically attached to the main body 12.
During installation, the pressure relief device 10 may be snap fit to a structure. Typically, a user presses on the four corners of the pressure relief device 10 in order to secure it within a reciprocal hole in a structure.
If liquid contacts or accumulates on the pressure relief device 10, the liquid passes to a drain hole or channel. Gravity and the vertical orientation of the pressure relief device 10 assist in draining or channeling the liquid from the pressure relief device 10.
In large vehicles, such as semi-trucks, conventional pressure relief devices are known to allow the intrusion of water or other liquids into the enclosed area due to the size of the device, and the amount of water present. For example, during a high pressure cleaning process, a substantial amount of water may accumulate on, and infiltrate past, the pressure relief device.
Moreover, if the membrane 16 or other such member flaps as air passes through the device 10, a noticeable flapping noise may be audible to an occupant of the vehicle. Some conventional pressure relief devices include sanoprene membranes, which, while providing an effective seal, are susceptible to producing an undesirable flapping noise. Also, the sanoprene membrane includes die cut tabs that are adapted to mate with slots provided in the housing. This arrangement has been known to leak. Further, the assembly process is cumbersome.
Other conventional pressure relief devices include foam-like membranes to minimize flapping noise. These devices include die cut holes adapted to fit over tabs provided in the housing. However, the foam membranes often tear or rip near the small die cut holes.
Still other conventional pressure relief devices include mechanical lock arms in the housing that are configured to mechanically capture the edge of the membrane. Typically, the edge of membrane includes holes or slots that fit over a mating member on the housing in order to assist in the assembly process. Once positioned, the lock arm is closed shut. Again, however, these devices are known to produce flapping noise and the assembly process is often cumbersome.
Other conventional pressure relief devices include a flap overmolded directly in the housing. While the assembly process may be less cumbersome than other designs, these devices still produce undesirable flapping noise.
Some conventional pressure relief devices include a deposit of plastic or rubber-like material near the flapper/housing interface to increase the robustness of the flapper, thereby minimizing flapping motion. However, the outer edge of the flapper or membrane may not seat firmly against the housing edge, which compromises the seal and can still produce an audible flapping noise.